# How to check an input String is a number or not in ruby?

**URL:** <https://www.ruby-forum.com/t/how-to-check-an-input-string-is-a-number-or-not-in-ruby/61229>\
**Category:** Rails\
**Created:** [May 22, 2006, 6:03am UTC](https://www.ruby-forum.com/t/how-to-check-an-input-string-is-a-number-or-not-in-ruby/61229 "2006-05-22T06:03:13Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![joshua-asem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e5b9ba/32.png) [@joshua-asem](https://www.ruby-forum.com/u/joshua-asem)\
**Post date:** [May 22, 2006, 6:03am UTC](https://www.ruby-forum.com/t/how-to-check-an-input-string-is-a-number-or-not-in-ruby/61229/1 "2006-05-22T06:03:13Z")

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How to check an input String is a number or not in ruby?  
Thanks in advance,  
Joshua

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**Author:** ![joshua-asem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e5b9ba/32.png) [@joshua-asem](https://www.ruby-forum.com/u/joshua-asem)\
**Post date:** [May 22, 2006, 6:53am UTC](https://www.ruby-forum.com/t/how-to-check-an-input-string-is-a-number-or-not-in-ruby/61229/2 "2006-05-22T06:53:43Z")

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Hi Joshua,

joshua asem wrote:

> How to check an input String is a number or not in ruby?

First, I’m going to assume you’re asking about how to do that in a Rails  
app  
as opposed to straight Ruby. If you’re looking for Ruby language  
support, a  
better place to ask your question would be  
[http://groups.google.com/group/comp.lang.ruby](http://groups.google.com/group/comp.lang.ruby)

You didn’t say whether you want / need to check it on the client- or on  
the  
server-side.

If server-side works for you, and it’s definitely the easiest, check the  
documentation on validates\_numericality\_of at  
[http://api.rubyonrails.org/](http://api.rubyonrails.org/).  
You’d use that validation in your model.

If client-side, you’ll probably want to use pattern matching in a  
Javascript. What pattern you’d validate against would depend on the  
format  
you’re expecting / allowing. The documentation at  
[http://api.rubyonrails.com/classes/ActionView/Helpers/JavaScriptHelper.html](http://api.rubyonrails.com/classes/ActionView/Helpers/JavaScriptHelper.html)  
should help you understand how to include the JS in your Rails app.

hth,  
Bill

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**Author:** ![joshua-asem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e5b9ba/32.png) [@joshua-asem](https://www.ruby-forum.com/u/joshua-asem)\
**Post date:** [May 22, 2006, 7:16am UTC](https://www.ruby-forum.com/t/how-to-check-an-input-string-is-a-number-or-not-in-ruby/61229/3 "2006-05-22T07:16:14Z")

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Hi,  
Thanks for your suggestion,  
But the exact thing i want is to validate using ruby script not the  
javascript and also not the validates\_numericality\_of. As I was coding  
differently little bit to support legacy database and without using the  
model directly. The results get returned from the stored procs in the  
hash form.  
So i just wanted to do it generally using ruby script.  
If you have the idea in ruby script , exactly the piece of code for  
validating number like isNumber(). Please reply with small piece of code  
if you don;t mind

Thanks in advance.  
joshua…

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**Author:** ![joshua-asem](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/e5b9ba/32.png) [@joshua-asem](https://www.ruby-forum.com/u/joshua-asem)\
**Post date:** [May 23, 2006, 6:17am UTC](https://www.ruby-forum.com/t/how-to-check-an-input-string-is-a-number-or-not-in-ruby/61229/4 "2006-05-23T06:17:54Z")

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On E, 2006-05-22 at 07:16 +0200, joshua asem wrote:

> if you don;t mind
> 
> Thanks in advance.  
> joshua…

You can use Integer(string\_containing\_number) which raises an  
exception if the string can not be converted to a number.

Or you could use a regular expression to check that the string  
only contains a number:

if string\_containing\_number =~ /^\d+$/

# is numeric, safe to use string\_containing\_number.to\_s

# (which would return 0 in case of failure to convert)

else

# not numeric

end

–  
Tarmo Tänav [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)